Ecology: Forest loss has biggest impact in pristine ecosystems

Nature

July 20, 2017

Intact ecosystems suffer greater biodiversity losses as a result of deforestation than those that have already been damaged or altered, according to a report in Nature this week. The study assesses the effects of deforestation in intact and human-modified landscapes on the extinction risk of over 19,000 vertebrate species worldwide, and identifies hotspots for extinction risks. The findings suggest that novel conservation efforts to protect intact forest landscapes are needed to prevent a new wave of extinctions.

Human-modified landscapes that have already experienced reductions in habitat availability are thought to have a higher risk of biodiversity loss than ecosystems that are largely intact, but some fragmented ecosystems have been shown to be surprisingly resilient. To determine whether conservation efforts should be directed towards intact or fragmented ecosystems, Matthew Betts and colleagues assess large datasets of global forest loss and extinction risk in 19,432 vertebrate species.
As expected, deforestation substantially increases the odds of a species being threatened with extinction. However, the risks are disproportionately higher in relatively intact landscapes than in already fragmented landscapes. For example, for every 1% rise in deforestation, the increased threat of extinction was over 10% higher in species from areas with high levels of forest cover (90%) than their counterparts in habitats with average forest cover (57%).

The authors find that some of the regions where biodiversity is at a particularly high risk include Borneo, the central Amazon and the Congo Basin. They predict that over the next 30 years, between 121 and 219 species in these regions (such as the Mendolong bubble-nest frog and the Mentawi flying squirrel) will become threatened with extinction under current rates of forest loss. Only 17.9% of these regions are currently formally protected, highlighting that areas considered to be of low vulnerability are actually at high risk of suffering species extinctions, the authors conclude.